"We stand with the people and the government of Nigeria, and call for those responsible to be brought to justice," Roth said.

According to media reports, gunmen targeted Christians at two separate churches in the northern part of the country, where Boko Haram has been active in the past. More than 30 people died in terrorist attacks on Christmas Day last year carried out by the Islamist group.

Pope Benedict XVI specifically mentioned Nigeria in his Christmas message, calling for an end to violence in that country.

Canada's Department of Foreign Affairs warns Canadians against non-essential travel to Nigeria, and just a few days before Christmas the U.S. State Department gave a similar warning to Americans "because of the risk of kidnappings, robberies and other armed attacks."